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# Lighting calculation need help

## Lighting calculation need help

#1
08-11-11, 08:45 PM
Member
Join Date: Aug 2011
Location: usa
Posts: 2
Lighting calculation need help

I have ( 20 x 100 ) 2000 sq/f, 9 feet high open area an i am planing to put some
new 2' x 4' fixtures with t-5 bulb's. My question is how many fixtures do i need and how many bulb's each one so the area can be bright more then average (very bright)
thanks

#2
08-12-11, 06:56 AM
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 14,093
When we do a space we figure 70 sq ft per T8 2x4 light. This is for separate offices.

By that number you would be looking at about 28 fixtures. However, if your using a standard ceiling grid the layout might not work out to look right. I did a quick layout and running the lights the short way (4' side running the 20' dimension) 4' off the walls and 4' in between the lay out looks good. But going with that down the 100' way, if you put 4' in between each light you end up with 32 lights. If you go 6' between each light you end up with 24 lights. laying out the lights the 4' going the 100' dimension does not give you a very good layout.

Some cases a 4 lamp fixture is the same price as a 3 lamp. If that is the case I would get 4 lamp. Maybe if you go 32 lights go with a 3 lamp. 4 lamp if you go 24 lights.

#3
08-12-11, 07:24 AM
Member
Join Date: Oct 2008
Location: New England
Posts: 9,460
Part of your very bright requirements will be a result of the color selection of the lamps, cool white to daylight. Also consider the color of the surrounding walls and ceiling. I once tested a cool white lamp in the same fixture as a daylight lamp and it looked like the cool white wasn't working properly, but it was.

There is also a shadow effect. If you will be sitting at a work bench and the light is behind you, you will not get good lighting directly in front. Separate bench lights are best, but if work positions are fixed, then placement of the overhead t-8's might be adjusted for the space needed.

Bud